Fake subpoenas harpoon 2,100 corporate fat cats

From phishing to whaling

A highly targeted email scam that singled out as many as 20,000 senior corporate executives on Monday resurfaced Wednesday as attackers sought to replicate their success installing identity-stealing software on the PCs of some of the world's most powerful individuals.

Like the first volley of emails, these latest messages masquerade as an official subpoena requiring the recipient to appear before a federal grand jury. The emails correctly address CEOs and other high-ranking executives by their full name and include their phone number and company name, according to Matt Richard, director of rapid response at iDefense, a division of VeriSign that helps protect financial institutions from fraud.

Recipients who click on a link that offers a more detailed copy of the subpoena are taken to a website that informs them they must install a browser add-on in order to read the document. Clicking "yes" installs a backdoor and key logging software that steals log-in credentials used on websites for banks and other sensitive organizations.

About 2,000 executives took the bait on Monday, and an additional 70 have fallen for the latest scam, Richard said. Operating under the assumption that as many as 10 percent of recipients fell for the ruse, he estimated that 21,000 executives may have received the email. Only eight of the top 35 anti-virus products detected the malware on Monday, and on Wednesday, only 11 programs were flagging the new payload, which has been modified to further evade being caught.

The group behind the attack is the same one that has launched other high-profile spear-phishing expeditions, in which a relatively small number of emails are tailored to their targets by including their names, titles and other personal information. The customization is designed to fool the recipients into believing they are legitimate. The practice of targeting CEO and other high-ranking execs is being dubbed as whaling.

The malware installed from Monday's attack caused infected PCs to report to a server based in Singapore. The updated trojan had machines reporting to servers in China, Richard said. In both cases, the IP addresses of attackers' servers were controlled by a group that goes by the name Piradius, among others.

The group is also responsible for attacks that use stolen customer lists to target individuals who have done business with a particular organization. That allows the attackers to masquerade as sales and support representatives from a company the recipient has a relationship of trust with, making it more likely the victim will agree to install malware or divulge sensitive information.

"That's probably one of their better attacks," Richard said. "It's extremely hard for them to pull off because they need to steal the customer database first."

In earlier attacks, the emails were more convincing because the English grammar and syntax were nearly flawless. The emails in most recent attacks were less polished, Richard said. ®